const fs = require('fs');

fs.readFile('./htmls/1.html',(err,data1)=>{
    if(err) throw err;
    fs.readFile('./htmls/2.html',(err,data2)=>{
        if(err) throw err;
        fs.readFile('./htmls/3.html',(err,data3)=>{
            if(err) throw err;
            console.log(data1 + data2 + data3)
        })
    })
})


const util = require('util');
const mineReadfile = util.promisify(fs.readFile);
async function main() {
    let data1 = await mineReadfile('./htmls/1.html');
    let data2 = await mineReadfile('./htmls/2.html');
    let data3 = await mineReadfile('./htmls/3.html');
    console.log(data1 + data2 + data3)
}

main()